feat(app): drop the known-words seed, and make a full wipe actually wipe

The seed pre-marked the artifact's 30 headwords secure on first run. Two
reasons it is gone rather than merely disabled:

It was never 30 cards. The match was on headword, and homographs each
carry their own lemma, so 그 as pronoun and as determiner both matched —
47 rows for a 30-word list.

Worse, "Reset everything" deleted the cards and then deleted the
'seed.known' guard along with the other meta keys, so the next boot
re-seeded and the deck looked untouched. The one thing a wipe exists for,
undone by the wipe itself.

Migration 5 clears the seed from installs that already have it. seedCard()
is the only writer that leaves updated_at = 0 on a card and the seed was
its only caller, so `DELETE FROM card WHERE updated_at = 0` removes exactly
the seeded rows and nothing the learner graded — the timestamp rule paying
for itself a second time.

test/domain/reset.test.ts pins both scopes: what a full wipe must leave
empty, what a roadmap reset must keep, that the deletions are tombstoned
so a sync cannot restore them, and that migration 5 really runs against a
schema-4 database rather than the test performing the delete itself.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

app/src/db/migrations.ts

@@ -133,6 +133,22 @@ export const MIGRATIONS: Migration[] = [
       CREATE INDEX IF NOT EXISTS tombstone_updated ON tombstone(updated_at);
     `,
   },
+  {
+    id: 5,
+    name: "drop the known-words seed — a new deck starts empty",
+    sql: /* sql */ `
+      -- The seed pre-marked ~30 headwords secure on first run. It made a
+      -- fresh install look like work already done, and because editReset
+      -- also cleared its 'seed.known' guard, a full wipe re-seeded on the
+      -- next boot: the one thing a wipe is for, undone.
+      --
+      -- seedCard() is the only writer that leaves updated_at = 0 on a card,
+      -- and the seed was its only caller, so this deletes exactly the seeded
+      -- rows and nothing the learner graded. Genuine reviews stamp the clock.
+      DELETE FROM card WHERE updated_at = 0;
+      DELETE FROM meta WHERE k = 'seed.known';
+    `,
+  },
 ];
 
 export const SCHEMA_VERSION = MIGRATIONS[MIGRATIONS.length - 1]!.id;

app/src/db/writes.ts

@@ -343,12 +343,12 @@ export async function editReset(db: Db, scope: ResetScope): Promise<void> {
       await tx.run("DELETE FROM peek");
       await tx.run("DELETE FROM surface WHERE lemma_id >= ?", [CUSTOM_LEMMA_BASE]);
       await tx.run("DELETE FROM lemma WHERE id >= ?", [CUSTOM_LEMMA_BASE]);
-      // Preferences, grammar flags and notes, trainer score, and the
-      // known-words seed marker. Device bookkeeping (schema_version,
-      // dict.*) is left alone — it describes this install, not the learner.
+      // Preferences, grammar flags and notes, and the trainer score.
+      // Device bookkeeping (schema_version, dict.*) is left alone — it
+      // describes this install, not the learner.
       await tx.run(
         `DELETE FROM meta WHERE k LIKE 'prefs.%' OR k LIKE 'grammar.%'
-                             OR k LIKE 'trainer.%' OR k LIKE 'seed.%'`,
+                             OR k LIKE 'trainer.%'`,
       );
     }
   });

app/src/domain/seed-known.ts

@@ -1,47 +0,0 @@
-/* The words the learner already had before the app existed.
-
-   Carried over from the artifact, which pre-marked these secure on first
-   run so the first review session was not thirty cards he could already
-   read. The list is his, not a curriculum artefact — it came from the
-   progress summary he wrote when the artifact was built.
-
-   Applied through seedCard(), which leaves updated_at = 0. That matters
-   twice over: it matches the artifact's own stampInit() behaviour, and it
-   keeps the seed invisible to sync — a fresh device seeding itself must
-   never look newer than the server's real history. */
-
-import type { Db } from "../db/types.js";
-import { seedCard, seedMeta } from "../db/writes.js";
-import { markKnown } from "@lib/srs.js";
-
-/** Verbatim from the artifact's SEED_KNOWN. */
-export const SEED_KNOWN = [
-  "나", "저", "너", "우리", "이", "그", "뭐", "왜", "누구", "어디",
-  "언제", "친구", "물", "밥", "책", "학교", "가다", "오다", "먹다", "마시다",
-  "좋다", "싫다", "크다", "작다", "슬프다", "진짜?", "잠깐만", "안 돼", "좋아", "싫어",
-] as const;
-
-const FLAG = "seed.known";
-
-/**
- * Mark the seed words secure, once. Returns how many matched a lemma —
- * some are phrases the dictionary may not carry as headwords, and a miss
- * is not an error.
- */
-export async function seedKnownWords(db: Db, today: number): Promise<number> {
-  const done = await db.get<{ v: string }>("SELECT v FROM meta WHERE k = ?", [FLAG]);
-  if (done) return 0;
-
-  const holes = SEED_KNOWN.map(() => "?").join(",");
-  const rows = await db.all<{ id: number }>(
-    `SELECT id FROM lemma WHERE headword IN (${holes}) AND source != 'custom'`,
-    [...SEED_KNOWN],
-  );
-
-  const card = markKnown(today);
-  for (const row of rows) await seedCard(db, row.id, card);
-
-  // Bookkeeping, not a user edit: unstamped, like the cards it guards.
-  await seedMeta(db, FLAG, String(rows.length));
-  return rows.length;
-}

app/src/state/store.tsx

@@ -24,7 +24,6 @@ import { bandForUnit } from "@shared/bands.mjs";
 
 import { ensureBands, loadManifest, recordProvenance, type DictManifest } from "../domain/dictionary.js";
 import { initProgress, readProgress } from "../domain/progress.js";
-import { seedKnownWords } from "../domain/seed-known.js";
 import {
   clearServerConfig,
   readServerConfig,
@@ -173,7 +172,6 @@ export function StoreProvider({
 
         // Needs the band rows present to match headwords, so it runs after
         // ensureBands. Seeded, so it carries no write timestamp.
-        await seedKnownWords(db, dayNumber());
 
         const rows = await db.all<{ k: string; v: string }>(
           "SELECT k, v FROM meta WHERE k LIKE 'prefs.%'",